Nowadays, systems in which a server provides content in response to a request from a client have been widespread, such as the World Wide Web (WWW) that provides documents of Hypertext Markup Language (HTML). With regard to such systems, shortening of time necessary to provide content for a client (specifically, shortening of time between transmission of a request from the client and output of content in the client) is a long-standing problem. For example, Patent Literature 1 describes a technology of caching content in a web server in order to efficiently use caches even if access to web services or memory resources is limited.